Philosophical Transactions. 147 



position not occur in still, rather than in running water, since radia- 

 tion would be more plainly manifested in the former, than in the 

 latter? The author answers, that " in still water, the hydrostatic 

 order which M. Arago has so well illustrated, as belonging to water, 

 when reduced to a temperature under 39°, has free play to establish 

 itself, and is not inverted by the mechanical action of a stream. 

 When the temperature of a body is under 39°, then the coldest por- 

 tions of it are the lightest, and naturally rise and float on the sur- 

 face. When, in a still pond, the water nearest the bottom has been 

 cooled below the general temperature, by contact with the solid 

 materials cooled by radiation, it is displaced by the heavier, warmer 

 water above. Hence, ice forms first on the surface, by the meeting 

 there of both the cold of radiation, and that acquired by contact with 

 the incumbent cold atmosphere." " In the rapids, the hydrostatic 

 order is overturned, and the colder, which is also the lighter water, 

 not only mixed with the warmer below, but at the whirls of the 

 greatest rapids, brought suddenly, without much mixing, into direct 

 contact with the bottom cooled still lower than itself by radiation. 

 If the water is at the temperature of 32° F., it can give out no heat 

 to the colder bottom without part of it being converted into ice, the 

 spiculae and crystals of which find a solid body for their attachment, 

 at the very point where the heat is given out." 



Discussion of Tide Observations made at Liverpool. 

 By John William Lubbock, Esq. 



This paper consists of a number of tables, drawn up from observa- 

 tions made at the London and St. Katharine's Docks. Those at the 

 former, are made by a person who notes the time when the water 

 has begun to fall, that is, has made its mark. The observations at 

 the latter, are made by noting upon a slate, (ruled for the purpose) 

 the height of the water, every minute before high water is expected, 

 all which, is afterwards copied into a book ruled in the same manner, 

 and the time of high water with the height, is easily inferred. The 

 height is ascertained, by means of a rod or tide-guage, connected 

 with a float, which is placed in a chamber, into which the water 

 enters through a culvert, so that the ripple or agitation of the water 

 in the river is avoided, as much as possible ; a clock carefully regu- 

 lated, stands close at hand. 



Experimental Researches in Electricity, 10th Series. 

 By Michael Faraday, D.C.L., &c. 



The object of this paper is to describe an improved plan of the voltaic 

 battery, and to develope some practical results, in reference to its 

 construction and use. In a simple voltaic circuit, the chemical forces, 

 which during their activity give power to the instrument, are gene- 

 rally divided into two portions ; the one of these is exerted locally, 

 while the other is transferred round the circle; the latter, constitutes 

 the electric current of the instrument, while the former, is completely 

 lost or wasted. The ratio of these powers varies ; thus, in a battery 



